They probably won't risk changing everything TOO much. It costs more time and money, and people might not like too many changes.
This should get a new thread though, as the sequels will be not exactly like what the third games of each gen were. Not entirely anyway.
I like finding out about all the new stuff, but I never really play the additional versions since IMO they don't add enough. And I can only be bothered to round up most of the mon once every generation, regardless of how many remakes and sequels they decide to spit out
They should make the battles go faster. And the message about the mons' Abilities slows them down even more. You can't efficiently skip through most of the text boxes, which can be quite annoying (just like healing your mon at the PokéCenter still takes too long).
Shaking Grass should be more frequent too. Plus, it's annoying when you walk over to it and trigger a random encounter before you make it there -- who wants to be forced to use a Repel for just 5 steps?
I did have a good idea to mix things up for the E4: instead of sticking with the same Types, we could have an E4 member with mon focusing highly on one or two stats: Attack and/or Special Attack, Defense and/or Special Defense, Speed, and HP (the bulky mon and the ones that like to heal a lot).
Similarly, the E4 or Gym Leaders could also set up their team around status ailments: there's Sleep, Paralysis, Poison, Burn, Freeze, Confusion, Love, and things like flinching (some moves have a high chance of this) and other hazards could come into play too. There's weather effects, of course, and abilities and moves that don't allow you to switch out your mon, or vice versa, force you to switch out (or switch out themselves with the likes of Baton Pass). There's also some moves and abilities that cause damage over time like from Leech Seed, Sandstorm, Stealth Rock, and barbs from a mon like Ferroseed, that hurt you when you do a physical attack on them. More than enough silliness to theme Gyms, E4, Teams and other people/places with.